Consulta retorna valores duplicados

Boa noite,

A query abaixo está mostrando alguns valores duplicados e outros errados:

SELECT c.contest_id, c.hacker_id, c.name,
SUM(s.total_submissions) as total_submissions,
SUM(s.total_accepted_submissions) as total_accepted_submissions,
SUM(v.total_views) as total_views,
SUM(v.total_unique_views) as total_unique_views
FROM concursos c
JOIN faculdades f ON f.contest_id = c.contest_id
JOIN desafios d ON d.college_id = f.college_id
LEFT JOIN view_stats v ON v.challenge_id = d.challenge_id
LEFT JOIN submission_stats s ON s.challenge_id = d.challenge_id
GROUP BY c.contest_id;

A saída deveria ser assim:

 contest_id | hacker_id | name   | total_submissions | total_accepted_submissions | total_views | total_unique_views |
+------------+-----------+--------+-------------------+----------------------------+-------------+--------------------+
|      66406 |     17973 | Rose   |               111 |                         39 |         156 |                56 |
|      66556 |     79153 | Angela |                 0 |                          0 |          11 |                 10 |
|      94828 |     80275 | Frank  |               150 |                         38 |          41 |                15

Mas está saindo assim:

 contest_id | hacker_id | name   | total_submissions | total_accepted_submissions | total_views | total_unique_views |
+------------+-----------+--------+-------------------+----------------------------+-------------+--------------------+
|      66406 |     17973 | Rose   |               222 |                         78 |         238 |                122 |
|      66556 |     79153 | Angela |              NULL |                       NULL |          11 |                 10 |
|      94828 |     80275 | Frank  |               150 |                         38 |          82 |                 30

Segue o link com uma amostra das tabelas: Amostras

Poderiam ajudar?

Grato